Terrible Vibration And A Noise

[Rocky MTN 2500HD]

I am new to this site and GM Trucks.

I just purchased a 2009 Sierra 2500 HD 4X4 6.0 Crew Cab SWB new.

The truck has 3k miles on it.

I have installed Leveling Keys and a 1" block in the rear.

Running 275/70-18 BFG's

 

Both with the changes and stock the truck has a VERY annoying sound like a spring or spring bar vibrating under the driver's side floor or under the dash. It sounds like when an older truck with a return spring on the clutch would vibrate. It happens at exactly 75 mph under light throttle or load and only in 6th gear.

I have looked at everything I can think of and can find nothing to account for the noise.

 

This past weekend while pulling a small snowmobile trailer (first time towing in 4WD) under acceleration the truck makes a terrible vibration like your driving on rumble strips.

If you let off the throttle or switch to 2WD the vibration goes away.

The vibration is very severe.

I'm not sure if the two conditions are related or not.

 

All U-Joints look good, no loose suspension components, etc.

The noise was there with the truck completely stock, but I had not towed with it stock to say if the vibration was present.

 

Anyone else experienced anything like this?

Thanks

[markw8]

This sounds like a job for your warrenty.

 

Mark.

[Rocky MTN 2500HD]

Just an update to hopefully save someone the aggrevation I've been through with the noise issue.....

There is a thick metal panel behind the plastic interior kick panel located directly under the steering column. It appears to be a shear panel to protect your legs in the event of an accident.

The metal portion is about 10 times heavier than the the plastic panel it is attached to and it's attached with plastic darts or nipples that are formed into the plastic panel.

All but one of the contact points were broken allowing the metal panel to vibrate or buzz causing the noise:(

 

Vibration is still there and I have the front driveline out to be balanced.

As to this being a warranty issue...... I agree, but they say they can't find a problem so before it turns into a mess I just want to get it fixed.

I really like this truck and want to get it right.

[RJG183SA]

Just an update to hopefully save someone the aggrevation I've been through with the noise issue.....

There is a thick metal panel behind the plastic interior kick panel located directly under the steering column. It appears to be a shear panel to protect your legs in the event of an accident.

The metal portion is about 10 times heavier than the the plastic panel it is attached to and it's attached with plastic darts or nipples that are formed into the plastic panel.

All but one of the contact points were broken allowing the metal panel to vibrate or buzz causing the noise:(

 

Vibration is still there and I have the front driveline out to be balanced.

As to this being a warranty issue...... I agree, but they say they can't find a problem so before it turns into a mess I just want to get it fixed.

I really like this truck and want to get it right.

You might want to check out this thread also

http://www.gm-trucks.com/forums/index.php?showtopic=109216